1. Field of the Invention
The present invention relates to a hub device for a bicycle, and more particularly, to a hub device for a bicycle for supporting a rotary motion of a wheel and serving to transfer the load from the wheel to a fork or the like which partially forms a frame.
2. Description of the Related Art
The generally employed hub device for a bicycle disclosed in Japanese Unexamined Patent Application Publication No. 2005-231501 includes a hub case which receives the load exerted to a rim to which the tire is fitted via a spoke, a bearing for rotatably supporting the hub case, and a shaft for receiving the load exerted to the hub case via the bearing and supporting the rotary motion of the hub case.
The aforementioned generally employed device is structured to employ a single row angular contact ball bearing as the bearing interposed between the shaft and the hub case. Accordingly, during traveling by bicycle, vibration or impact resulting from running on the rough road surface may be exerted to the above-structured bearing from the wheel. The exerted load owing to such vibration and the like may cause the risk of damaging the bearing or the hub case.